The cyclic stress—strain response and dislocation structures of Cu-16 at.%Al alloy II: Polycrystalline behavior

Laird, C.; Stanzl, S.; Veaux, R. de la; Buchinger, L.

doi:10.1016/0025-5416(86)90193-x

Cited by 40 publications

(6 citation statements)

References 17 publications

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“…Until now, dislocation arrangements have been studied mainly using TEM e.g. in the case of single crystals of Cu-Zn [38] and Cu-Al [39] alloys. Buchinger et al [40] found dislocation arrangements corresponding to localization of the cyclic plastic strain -so-called "persistent" Lüders bands.…”

Section: Imaging Of Dislocation Arrangements After Fatiguementioning

confidence: 99%

Case studies on the application of high-resolution electron channelling contrast imaging – investigation of defects and defect arrangements in metallic materials

Weidner

Biermann

2015

Philosophical Magazine

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In 1967, Coates discovered the electron channelling contrast of backscattered electrons (BSEs) in scanning electron microscopy, and by this the possibility to investigate arrangements of lattice defects in deformed microstructures of materials. Since that time, a straightforward development of the scanning electron microscopes as well as of the electron channelling contrast technique took place. Nowadays, the performance of scanning electron microscopes is high enough that the resolution of electron channelling contrast imaging (ECCI) micrographs is comparable with conventional bright field transmission electron microscopy (TEM) micrographs. In the first part of the present paper, a historical review on the development of the ECCI technique starting from its discovery more than 45 years ago up to the combination with other advanced methods of scanning electron microscopy like electron backscatter diffraction or high-resolution selected area channelling patterning in the last few years is given. Major important investigations using this technique for the visualization of individual lattice defects like stacking faults (SFs) and dislocations or dislocation arrangements are chronologically summarized. The second part demonstrates that nowadays, ECCI micrographs taken in high-resolution scanning electron microscopes can be called high-resolution ECCI (HR-ECCI). It is shown that the resolution of individual SFs and dislocations in the HR-ECCI micrographs is comparable to that of conventional TEM (about 15 nm defect image width). Furthermore, the paper is demonstrating that HR-ECCI micrographs can be obtained for various types of materials after different mechanical loadings and different grain sizes ranging from large grain size of 500 μm (cast steel) down to less than 2 μm (γ-TiAl).

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Section: Imaging Of Dislocation Arrangements After Fatiguementioning

confidence: 99%

Case studies on the application of high-resolution electron channelling contrast imaging – investigation of defects and defect arrangements in metallic materials

Weidner

Biermann

2015

Philosophical Magazine

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“…In polycrystalline materials, grain boundaries contribute to local stress concentration, produced by incompatibilities of both elastic and plastic variants, which may serve as crack initiation sites 23 . Figure 2 shows the surface of a polycrystalline Cu–16 at.% Al alloy.…”

Section: Experimental Set‐up Of An Ultrasonic Fatigue Machinementioning

confidence: 99%

“…Additionally, strain rate sensitivity of alloys is usually much smaller than that of pure metals 36 . Investigations on the dislocation structure and cyclic stress–strain response of Cu single crystals and Cu–Al single and polycrystalline material verified that essentially similar deformation and fracturing features exist for high and low testing frequency 18 –23 …”

Section: Ultrasonic Torsion Fatiguementioning

confidence: 99%

Fracture mechanisms and fracture mechanics at ultrasonic frequencies

Stanzl-Tschegg¹

1999

Fatigue Fract Eng Mat Struct

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Performing fatigue tests at ultrasonic frequencies, e.g. 20 000 Hz, allows one to perform experiments beyond 109 and 1010 cycles within half a day or a week, respectively. The testing technique has led to the construction of fatigue machines of high technical standard. Use of the ultrasound technique to study the mechanisms of crack initiation in pure metal single crystals, in cast alloys with voids being crack initiation sites, and in complicated fibre‐reinforced laminates is reported. Likewise, use of ultrasonic loading to study the mechanisms of crack propagation is discussed, as well as LEFM principles; especially when these principles cannot be applied. It is shown how crack growth retardation with increasing crack length is attained in fibre‐reinforced laminates by the effect of fibre bridging. Additional experimental possibilities, e.g. random loading, variation of mean load, superposition of shear loads, variation of temperature and environment, and not only axial but also torsional loading at ultrasonic frequency, and recent research results are discussed.

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“…The hardness in the A section of the FGHAZ was slightly higher than that of the B section and C section; but the difference in the hardness among these three regions was not distinctive. It is well known that in metallic materials, there is a close connection between changes in the hardness and the dislocation motion . Because the variation in the hardness at these three surfaces was small, it was concluded that the difference in the void size at these three different sections was not derived from a change in the dislocation density.…”

Section: Resultsmentioning

confidence: 98%

Effect of multiaxial stress state on creep damage in ASME T92 welded joint

Wang

et al. 2019

Fatigue Fract Eng Mat Struct

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This study reports the type IV fracture process and the influence of multiaxial stress state in ASME T92 welded joints during creep. The type IV fracture occurs at the fine‐grained heat‐affected zone (ie, FGHAZ), involving void initiation, growth, and coalescence, microcrack occurrence, propagation and extension, and eventual macrocrack with consequent joint failure. The creep damage is not uniformly distributed along the thickness direction in the FGHAZ, and the central part of the welded joint is the most seriously damaged region. The equivalent creep strain is higher at the external surface, but the stress triaxiality is larger in the centre section. Large equivalent creep strain could promote creep void initiation, whereas high hydrostatic pressure and stress triaxiality factor accelerate void growth in the FGHAZ of T92 joints. Besides, reducing groove angle and HAZ width of the joints is recommended to delay the occurrence of type IV cracking because of lower equivalent creep strain and stress triaxiality factor.

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The cyclic stress—strain response and dislocation structures of Cu-16 at.%Al alloy II: Polycrystalline behavior

Cited by 40 publications

References 17 publications

Case studies on the application of high-resolution electron channelling contrast imaging – investigation of defects and defect arrangements in metallic materials

Case studies on the application of high-resolution electron channelling contrast imaging – investigation of defects and defect arrangements in metallic materials

Fracture mechanisms and fracture mechanics at ultrasonic frequencies

Effect of multiaxial stress state on creep damage in ASME T92 welded joint

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